Preheat your oven to 350, then spray an 8" square baking pan with non-stick spray.
Mix graham cracker crumbs and butter until moistened.
Press cracker crumbs into the bottom of the pan.
Mix cream cheese, sugar, and vanilla.
Beat in yogurt, egg whites, lemon juice, and flour.
Pour over graham cracker crust.
Stir jam and drop by small spoonfuls on top of the filling.
Use a knife to gently swirl the jam and create a marble effect.
Bake for 25 to 30 minutes.
Cool to room temperature.
Chill for 3 hours.